Epidemiological Models Can’t Tell States When to Open or How

With more than a dozen states starting to relax mandatory social distancing edicts, some organizations are offering advice to states on when they might prudently alleviate or decentralize current mandates. The most ambitious effort is an offshoot of a model from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington. Having been made famous in White House briefings by Doctors Birx and Fauci, that “Murray Model” could conceivably be influencing federal and state official about the proper timing and design of state decisions to relax mandates.

I assembled a table “Evaluating State COVID-19 Rules” to examine IHME recommended dates for states to begin “opening up” businesses, shopping, recreation and employment, while adding two sources of relevant facts.

The first column in the table shows COVID-19 deaths per million by state. The national average death rate is 179 per million, yet 31 of the 50 states have experienced fewer than 60 deaths per million. On the basis of experience, these 31 states (at least less‐​populated counties within the states) appear to be relatively low‐​risk places to experiment with relaxing restrictions.

The second column shows the Reproduction Rate (Rt) in the latest week. In this series, “(Rt) represents the effective reproduction rate of the virus.” That is, if each person affects one other then Rt equals 1. The curve is then flat, since everyone cured is matched by someone newly infected. While Rt is below 1.0, on the other hand, that means new cases are smaller than the number cured so the number still infected is declining.

By the week ending April 25, 42 states had an Rt below 1.0. Among some of the first to lighten restrictions, Rt was down to 0.83 in Florida and Oklahoma by April 30, 0.78 in Georgia and 0.75 in Texas.

Soon after famously projecting that U.S. deaths would total only 60,000­ –a number already exceeded­– the IHME model’s latest update “raises the outlook for the cumulative U.S. death toll through Aug. 4 … to a new figure of 74,073.” The new curve projects that nationwidedaily deaths will drop to 0–10 by July 1. But that is said to depend on maintaining “current social distancing… until infections [are] minimized and containment implemented.” That may explain why these modelers recently began advising states what to do and when to do it. “A recent analysis from the Institute for Health Metrics and Evaluation,” noted an April 22 local news story, “suggests that Oklahoma may be among several states that need to continue social distancing until late June or early July.” Oklahoma Governor Kevin Stitt ignored that advice and allowed haircuts.

The IHME team created a 1–6-point scorecard awarding the most points for the most severe “current social distancing” rules. They use these scores to propose specific dates in May‐​July when each state is granted approval to begin graduating from business and school closures and universal home isolation to more‐​targeted “containment strategies… [such as] testing, contact tracing, isolation, and limiting gathering size.”

The table’s third column “IHME Opening Date”– shows when “relaxing social distancing may be possible with containment strategies.” The last column shows each state’s “IHME Score,” which I argue is mainly what determines each state’s date for relaxing “social distancing” as they define it.

The modelers “evaluate [State] government‐​mandated social distancing measures… based on the New Zealand Government alert system Level 4″ (which was eased to Level 3 on April 28). They rate the virtue of states by how many of six equal‐​weighted broad categories of restrictions they implemented. A perfect score of 6 would require (1) closing nonessential businesses, (2) closing nonessential services, (3) closing all schools, (4) banning large gatherings, (5) issuing stay‐​at‐​home orders, and (6) “travel severely limited.”

No state scored more than 5, because no state could meet the New Zealand standard for domestic or international immobility. New Zealand banned foreign travelers on March 12 (because 5 people died out of 4.8 million) following other island nations Hong Kong and Singapore. New Zealand’s March 23 Level 4 plan also decreed “Public transit is closed.” Period.

Since no U.S. state lived up to New Zealand’s travel and transit bans, that left the highest possible score at 5. As a result, the unparalleled risks of proximity to strangers in New York’s subways, trains, busses and airports became irrelevant to scorekeepers who granted New York the same 5‐​point safety score as states with no mass transit or international airports. So, the IHME gives New York its blessing to relax social distancing after May 27. All others states that checked five boxes are likewise sanctioned to open in May, some a week or two earlier.

States with a score of 4, on the other hand, have to wait until June before doing anything different. And states with a score of 2 or 3 have to wait until July when the IHME model predicts zero COVID-19 deaths nationwide (we may not believe that, but they should because it’s their model).

In short, the timing recommended for opening a state’s economy depends on points earned on the basis of adherence to New Zealand’s formerly tough rules. However, the IHME makes a contrary claim that the “timeline is based on the date by which our model projects that COVID-19 infections will drop below 1 per 1 million people.” Yet the model projects only deaths per day, not “infections” (most of which are asymptomatic and uncounted) or even cases (which are sensitive to testing). Also, the model tracks actual deaths, not deaths per million.

Even if the dates for relaxing social distancing depended on projected deaths falling to 1 per day (rather than infections per million) that goal has been met by South Dakota ever since April 8 which you might think would make the state safe to open up entirely. South Dakota never closed anything but schools and large gatherings, in fact, which is why it is cursed with the lowest IHME score of 2. So, this remarkably safe state is admonished by the IHME to keep its two little rules in place until “after July 5, 2020.”

The fact that some states have a larger number of social distancing rules cannot explain why some had fewer deaths than others. On the contrary, South Dakota and 18 other states had fewer than 60 deaths per million regardless of their sub‐​par IHME scores of 2–4 and their resulting late dates for changing current rules in any unapproved way (such as confining home isolation to the sick and vulnerable)

Policies to deal with epidemics should be evaluated more on actual results and less on illusions that anyone really knows which schemes will prove more cost‐​effective and durable than others.

After graphically comparing mitigation policies with results among many states and countries, and finding no clear connections, Yinon Weiss concluded that “legal shut downs may only play a small role in the slowing down of the spread when compared to other factors such limiting travel to/​from hot spots, degree of public transportation use, washing hands, cancelling high transmission events such as conferences, and whether people are staying home when sick or exposed.”

The first columns of my table provide two relevant measures to discern how well states are actually coping with COVID-19, rather than relying on malleable model projections or subjective points scored in the IHME 1–5 virtue award contest. New tests, cases, hospitalizations and deaths also bear watching for potential hot spots, of course. Thankfully, no infectious disease has ever before been so quickly and transparently monitored by so many private and state online trackers.

If federal or state officials are instead considering relying on dates and scores from the University of Washington’s IHME team to decide what to do and when to do it, they should carefully reconsider delegating such authority to unaccountable technocrats to make social, health and economic choices that will deeply affect many millions of American lives.